Honors AB Pre-Calculus
Burkett
Activity:
An Afternoon in the City
Objective:
Students will be able to determine and describe increasing, decreasing and constant intervals for
a given function.
Overview:
Students will analyze a graph (time vs. distance from school) and determine from the graph,
when they are getting farther away from school, closer to school or staying the same distance
from school.
In a class discussion these phrases will be connected to the vocabulary from the unit. Students
will then write a detailed story about the afternoon adventure depicted in the graph.
Next, students will be given graphs of polynomial functions and will be asked to determine
increasing and decreasing intervals as well as relative minimums and maximums.
Finally, students will be given the graph of electric usage vs. time and will be asked to determine
increasing and decreasing intervals as well as relative minimums and maximums and explain
them in the context of the situation.
Important Discussion points:
 In a class discussion connect phrases in activity to the vocabulary from the unit
(increasing, decreasing, constant).
 Discuss the x-axis as the “the interval” and the y-axis as the “when it is increasing,
decreasing, constant”.
 When students look at the polynomial function graph
o discuss the ends – students may mark these as low points or high points…students
may make the end of the intervals finite values.
o discuss whether to use < or < etc.
 After Part III, reiterate the terms relative minimum and relative maximum
Data used to create the graph:
Sequence of Places Distance from Distance between Time between
Payton (miles) places (miles) places (minutes)
Payton 0 0 0
Eat – a - Pita 0.23 0.23 4.09
Art Institute 2.46 2.59 46.04
Virgin Records 1.18 2.08 36.98
Garrett Popcorn 1.00 .17 3.02
Water Tower Place 0.93 .26 4.62
Grant Park 1.94 1.2 21.33
Navy Pier 1.8 1.42 25.24
Payton 0 1.8 32
Time was determined by the fact that an average youth walks 4.95 feet per second = 0.05625
mi/min
Part II Instructions
Write a detailed story about you and your friends’ adventure that afternoon. Be sure to include
in your story where you went, how long you stayed there and how your distance from Payton
was changing during your excursion. Be creative!
Honors AB Pre-Calculus
Burkett
About the energy consumption graph
(from: http://www.seattlecentral.org/qelp/sets/042/042.html#About):
The use of electricity by municipalities varies throughout the day in a cyclic or periodic fashion. Energy use is
lowest in the early morning and peaks at the breakfast and dinner/evening hours when energy sapping activities such
as heating, cooking, washing and lighting (using resistance devices) are in full swing. Superimposed on this daily
variation are trends in energy consumption reflecting changes in the weather (heating or air conditioning), longterm
net changes in energy efficiency, etc.
The diurnal variation in energy consumption can present challenges to utilities, which must design production and
delivery systems that can handle peak loads much higher than the mean load. In addition, it may not be possible to
adequately curtail the energy generation system during the early morning hours of low consumption; hard to shut
down nuclear power plants and hydroelectric dams for a few hours. Energy utilities often lower their rates for off-
peak usage, to encourage consumption of otherwise somewhat "wasted" energy. Pumped hydrostorage facilities take
advantage of these price differentials, to create potential energy during off peak hours when energy costs are low,
and then to release that potential energy during peak hours when costs are high, thereby generating a profit despite a
net loss in system energy.
The data in the table and graph represent 4 days of electric usage from one delivery point in New Hampshire at
the end of August, 1997. The consumption values (in kilowatt-hours) also include losses of electricity in the
distribution system (transmission lines are not 100% efficient). The diurnal cyclic behavior dominates the data,
however the numbers are not completely sinusoidal; electricity consumption drops around mid-day to early
afternoon. Why? The lowest consumption rate seems constant over this 4 day period, but the 4th day's maximum
usage (September 1, 1997) seems much higher than the previous 3 days. What might have caused this spike?
The data could be modeled with a simple sinusoidal function of ø. Students must choose a midpoint in the cyclic
data for ø = 0, and a value for the maximum (or minimum) difference from the midpoint; some iteration will be
required. Are the data symmetric like a sinusoidal function, or is there some asymmetry to the data? The residuals
from the model might prove interesting.
Reference: data from the New Hampshire Electric Co-Op http://www.nhec.com/index.html
Honors AB Pre-Calculus
Burkett
Name_______________________
An Afternoon in the City
THE SCENARIO:
You and your friends decide to go on an afternoon excursion after seminars. You leave Payton
at 11:30 am. The graph below shows how far you are from Payton as a function of how much
time has passed since you left school. The letters on the graph indicate the places you visit on
your excursion:
A – Eat – a – Pita E – Water Tower Place
B – The Art Institute F – Grant Park
C – Virgin Records Mega store G – Navy Pier
D – Garrett Popcorn Shop H - Payton
Part I
1) What does the x-variable represent (hint: look at the x-axis)?
2) What does the y- variable represent (hint: look at the y-axis)?
3) At what time do you get to the Garrett Popcorn Shop? How far are you from Payton at that
time?
4) During what time periods are you getting further away from Payton (you can approximate)?
How were you able to determine these intervals from the graph?
5) Darken thee sections of the graph you listed in #4 with a red colored pencil.
6) During what time periods does your distance from Payton stay the same (you can
approximate)? How were you able to determine these intervals from the graph?
7) Darken the sections of the graph you listed in #6 with a blue colored pencil.
8) During what time periods are you getting closer to Payton (you can approximate)? How were
you able to determine these intervals from the graph?
Honors AB Pre-Calculus
Burkett
9) Darken the sections of the graph you listed in #8 with a green colored pencil.
10) Which axes did you look at to determine when were getting closer to Payton, further away
from Payton, or staying the same distance away from Payton?
11) Once you determine the correct interval, which axes did you look at to determine the time
periods for questions 4, 6, and 8?
Part II
Your teacher will give you instructions for this part.
Part III
For the graph you are given do the following:
1) Darken each increasing interval with a red colored pencil
2) Mark the section of the x-axis that is below (or above) that interval the same color.
3) Darken each constant interval with a blue colored pencil
4) Mark the section of the x-axis that is below (or above) that interval the same color.
5) Darken each decreasing interval with a green colored pencil
6) Mark the section of the x-axis that is below (or above) that interval the same color.
7) Put a big black dot at each of the high points on the graph
8) Put a big yellow dot at each of the low points on the graph
9) List the increasing intervals below. Give your answer as a compound inequality
(ex. -3 < x < 5)
10) List the decreasing intervals below. Give your answer as a compound inequality
(ex. -3 < x < 5)
11) List the constant intervals below. Give your answer as a compound inequality
(ex. -3 < x < 5)
12) List the high points (called relative maximums) below. Give your answer as an ordered
pair (ex. (-3, 5))
13) List the low points (called relative minimums) below. Give your answer as an ordered
pair (ex. (-3, 5))